Description of an ultrasound-guided rectus sheath block injection technique and the spread of dye in calf cadavers

Clinical efficacy of an ultrasound-guided bilateral rectus sheath block for umbilical hernia repair in calves: A prospective randomized trial

“…The present study describes an ultrasound-guided, transverse, in-plane rectus sheath injection with methylene blue in calf cadavers and its clinical efficacy in providing perioperative analgesia after herniorrhaphy under general anesthesia in field conditions. Our study confirmed that the plane between the rectus abdominis muscle and its internal sheath could be easily identified and targeted with high-frequency ultrasonography using an in-plane technique, as described by Ferreira et al ( 25 ). Moreover, we found that bilateral RSB with 0.25% bupivacaine HCl, with the addition of 1 µg/ml dexmedetomidine HCl, improves postherniorrhaphy analgesia in calves receiving a postoperative dose of flunixin meglumine IV.…”

“…The other hypothesis that may explain why a smaller volume per unit of body weight was sufficient to provide perioperative analgesia is that, in a given species, the increase in body weight with aging is associated with a reduction of surface area per unit of body weight (38). In other words, the body surface area of our calves, weighing on average over 130 kg, was proportionally smaller than that of calves used by Ferreira et al (25), potentially allowing for more ventral branches of spinal nerves stained.…”

“…Injection within the rectus sheath has recently been described in 16 calf cadavers using either 0.25 or 0.5 ml/kg 1% methylene blue per hemiabdomen ( 25 ). The technique used was similar to the one described in the present work.…”

“…To identify the rectus abdominis muscle, the transducer was initially placed in a transverse orientation to the midline to identify the linea alba before sliding it laterally to the umbilicus. The area was scanned in a medial-to-lateral direction until the following landmarks could be visualized: (1) the lateral aspect of the rectus abdominis muscle; (2) the twin "tram" lines representing the internal lamina of the sheath of the rectus abdominis muscle and the transversalis fascia; and (3) the peritoneum (24)(25)(26). Once the operator became confident with the ultrasound anatomy, a 22-gauge, 90-mm spinal needle (Spinale Quincke, PicIndolor; Artesana S.p.A., Italy) was introduced in a lateral-to-medial orientation and at a 30°angle with the in-plane technique.…”

“…In a more recent prospective, blind study, RSB appeared to improve postoperative analgesia and pain scoring with respect to the sole local anesthetic infiltration in a similar population ( 23 ). To our knowledge, the anatomy of the RSB has been described in thawed canine ( 24 ) and bovine ( 25 ) cadavers, but its clinical efficacy has never been tested in veterinary species.…”